Patient-Side Giardia spp Diagnostics
Lindsay A. Starkey, DVM, PhD, DACVM, (Parasitology), Auburn University
In the Literature
Symeonidou I, Gelasakis AI, Miliotou AN, et al. Rapid on-site diagnosis of canine giardiosis: time versus performance. Parasit Vectors. 2020;13(1):544.
The Research …
Giardia spp can be difficult to visualize on fecal flotation or direct smear, as they are very small, may be present only intermittently, and can be confused with other material (eg, yeast, pollen). In addition, some flotation solutions can cause Giardia spp cysts to distort or rupture, hindering recovery and identification. Additional tests (eg, immunoassays, molecular testing) to help accurately detect and diagnose infection have been developed.
This study* compared an in-clinic Giardia spp immunochromatographic strip test (IST) with double-centrifugal fecal flotation in zinc sulfate. Both tests were then compared with PCR and ELISA testing, which are the gold standards for detection.
Samples from 100 dogs with diarrhea were analyzed. IST detected 50 positive and 50 negative results.
Of the IST-positive samples, Giardia spp cysts were detected via flotation in 34 samples. Cysts were not microscopically visible in any of the IST-negative samples. All 50 IST-positive samples also had positive ELISA and PCR results.
Of the 50 samples that were negative on IST and fecal flotation, 22 had positive PCR results and 15 had positive ELISA results; 8 samples tested positive with both ELISA and PCR.
Although false-negative results occurred with IST and fecal flotation compared with the gold standard tests, IST identified more positive samples than traditional flotation. These findings add to the body of evidence that patient-side immunoassays are valuable clinical tools for aiding in the diagnosis of Giardia spp infection.
… The Takeaways
Key pearls to put into practice:
Giardia spp can be challenging to detect, but an accurate patient-side diagnostic test can help.
Fecal flotation remains an important diagnostic tool, as parasites other than Giardia spp can cause or contribute to diarrhea and will not be detectable with a patient-side Giardia spp test.
Using a combination of diagnostic tools is more likely to produce an accurate diagnosis.
*This study was partially funded by Virbac.